This invention relates to a roll paper feeding apparatus for an electrophotographic processing machine which is adapted to prepare a negative plate (offset master) for offset printing.
Electrophotographic processing machines are employed for preparing offset masters by means of an electrophotographic method and its use is now widespread in the field of printing and presswork due to the simplicity of handling and opertion thereof and the like. A master paper (photosensitive paper) used for an offset master comprises lining, underlining and photoconductive layers successively laminated on a support and is electrified so as to provide the photoconductive layer with photosensitiveness.
FIG. 1 is a structural view showing in section one form of a console type electrophotographic processing machine which has been conventionally used. As shown, the console type electrophotographic processing machine has a main body 40 which is provided upwardly and forwardly thereof (in the direction of an arrow F as shown) with a photographing means 41. The photographing means 41 is formed forwardly of the top thereof with a document tray 411 for holding documents (not shown) and is adapted to prepare a printing stencil plate. The document tray 411 is designed to open forwardly and rearwardly of the main body 40 such as to carry documents thereon. The document tray 411 is provided downwardly thereof with an exposure lamp 412 adapted to expose the document surface carried on the tray, and a photographic lens 413 for condensing photographic light which is exposed by the exposure lamp 412 and reflected by the document surface for image formation. The photographing means 41 is composed of the document tray 411, the exposure lamp 412 and the photographic lens 413.
On the other hand, the main body 40 of the electrophotographic processing machine is provided upwardly and rearwardly thereof (in the direction of an arrow R as shown) with a master paper supply unit 42 for receiving therein a roll of photographic processing copying paper (hereinafter referred to as master paper) such as paper formed of for example, zinc oxide. On the top of the master paper supply unit 42 is mounted a master paper loading cover 421 which is opened when the roll of master paper P is loaded. The master paper supply unit 42 is also provided with a cutter 422 for cutting a predetermined length of the master paper P to be fed in the direction of an exposing means and a corona charged device 423 connected thereto for electrifying the master paper P as cut. A suction type exposure bed 43 is provided downwardly of the master paper supply unit 42 such as to hold the master paper P which is thus cut in predetermined lengths, electrified and conveyed in the direction of an arrow C as shown for image formation. Downwardly of the photographic lens 413 is mounted a mirror 44 which is arranged to reflect a photographic light from the document surface and then expose the master paper P absorbed and held by the front surface 43A of the exposure bed 43. The exposure bed 43 is provided downwardly thereof with a developing unit 45 for developing the exposed master paper P, and a fixing unit 46 connected thereto and adapted to fix and process the developed master paper P. A developing and fixing is processed by these units, the master paper P is discharged out of a master paper take-up port 47 formed downwardly of the front surface of the main body 40. A power source unit 48 is counted downwardly of the rear thereof to drive the entirety of the instant apparatus.
In this connection, it is noted that while the supply unit for the master paper P is shown in FIG. 1 as being for one roll, a double line supply unit may be fabricated by means of which the paper is fed through upper and lower rolls.
In such an electrophotographic processing machine, irregularity derived from cutting the tip of the master paper P or a portion thereof stained with dirt from hands is cut away when a new roll of the master paper P is installed so that it is necessary to feed the master paper P without dirtiness and in an unchanging condition.
For the accommodation of the aforementioned requirement, as shown in FIG. 2 (in this instance, the paper has been conventionally trained in a double line over upper and lower rolls 50 and 51), the master paper PU fed from the upper roll 50 has been conveyed through nip rollers 52 and 53 to a cutter 422 whereas the other master paper PD from the lower roll 51 has been transported through nip rollers 55, 56 and 53 to a cutter 422. Exposure of each of the rolls of master papers PU and PD starts at a position A. For example, when the tip of the master paper PU rolled off the upper roll 50 assumes the position A while the tip of the master paper PD rolled off the lower roll 51 is located at B2 on standby, the upper roll 50 can be removed due to shortage of paper and a fresh upper roll 50 loaded. Upon actuation of a start switch (not shown) for cutting the tip of the paper rolled off the newly loaded upper roll, the master paper PU is conveyed through the nip rollers 52 and 53 to a position where a cutter 422 is provided. Further, the master paper PU is conveyed for a predetermined distance (for example, more than about 600 mm as a whole) and its conveyance is terminated when the tip of the paper reaches the exposure bed 43 and is held in an absorced condition. At the same time, the cutter 422 is actuated to cut off the tip of the paper. Thus the cut paper tip end as absorbed on the exposure bed 43 is manually taken by the operater out of a take-up port (not shown) mounted on the exposure bed. After cutting and disposing of the tip of the master paper PU, the next tip of the master paper PU is returned to a position designated at 81 and is then kept on standby when the start switch is operated. Simultaneously the tip of the master paper PD which is rolled out of the lower roll 51 and held on standby is conveyed to the position A. Subsequently, the master paper is transported by predetermined distance and cut by the cutter 422.
Such a conventional electrophotographic processing machine has involved disadvantage in that the length of the tip cut from the master paper is more than about 600 mm which involves a great amount of loss and a high cost for the photographic processing. Labor is inevitably required for discarding paper tips every time the start switch for cutting off the paper tip is depressed, so that operability is lowered. Difficulty is involved in simultaneously conducting photographic processing with shifting the position of the paper tip incidental to the shifting of the upper and lower rolls.